After the T-Virus infects a human being, it causes a decline in brain activity. Should the new zombie be incapacitated, after a time its tissue regenerates. The T-Virus causes further necrosis and terrible blood seepage, giving the zombie its crimson skin, small claws, increased resistance to firearms, slightly increased intelligence and a more aggressive attitude. Capable of running and jumping, a Crimson Head presents a significant threat.

The process is only halted by incinerating, decapitating, or the destruction of legs of the fallen zombie, thereby destroying any possibility for regeneration and mutation. If a Crimson Head mutates further, it will eventually become a Licker.

The Crimson Head made its initial appearance in the Resident Evil remake. It did not feature in the original version. The first one encountered beneath the Spencer cemetery inside a hanging coffin is the original prototype, otherwise known as the Elder.